There are known various types of travel assistance devices for wheelchairs, utilizing tracks for travel along surfaces that prohibit wheeled travel therealong. Such devices include wheelchairs having a built-in auxiliary tracked travel facility, tracked carrier devices for conveying wheelchairs along stairways, and travel devices employing tracks only.
An indication of the state of the art is found in the references that follow.
German Patent No. 3,617,518, describes a wheelchair having both wheeled and tracked travel means. The tracked means is permanently mounted on the wheelchair, and no means are provided for readily decoupling the tracked means from the wheelchair.
U.S. Pat. Nos. 4,671,369, 4,674,584 and 4,915,184 describe a wheelchair having both wheeled and track belt travel means. The described wheelchair is purpose-built and is not readily collapsible. Additionally, the track belt travel means, being an integral part of the wheelchair, is a permanent feature thereof, and is thus not readily detachable therefrom.
The following publications describe wheelchairs having integral wheel and track means. The publications are U.S. Pat. No. 3,198,534; U.K. Patent No. 693,983; and German Patent No. 3,827,607. In all of the devices described in the foregoing publications, the track means are neither readily couplable to nor decouplable from the remainder of the wheelchair.
The following publications describe wheelchairs having track means for selectably engaging inclined surfaces, such as stairways, thereby permitting travel therealong. The publications are: published French Patent Application No. 2,615,100; U.S. Pat. No. 3,191,953; published German Patent Application No. 3,827,607; U.S. Patent Nos. 3,602,522, 3,111,331, and 3,146,841. In none of the devices described in the foregoing publications are the track means either readily couplable to or decouplable from the remainder of the wheelchair.
Published German Patent Application No. 3,150,193 relates to a purpose-built vehicle having wheeled travel means and selectably deployable tracked travel means.
The following references relate to stair climbing wheelchair carriers: U.S. Pat. Nos. 4,432,426; 4,401,178; 4,566,550; 4,566,706; and 4,771,839; published European Patent Application No. 0,213,394; and Canadian Patent No. 1,150,333. In each of the references, a carrier travels on powered tracks, and is configured to support a wheelchair. With guidance from an operator, the carrier, together with the wheelchair and a person seated thereon, may be driven along a stairway. The wheelchair must be removed from the carrier before wheeled travel can be resumed.
U.S. Pat. No. 4,898,256 describes a further stair climbing wheelchair carrier. The carrier, which travels on powered tracks, is configured to receive a wheelchair and, with guidance from an operator, the carrier, together with the wheelchair and a person seated thereon, may be driven along a stairway. The main travel wheels of the wheelchair may be retained in contact with a ground surface so as to permit limited use of the wheels, so long as the tracks are in a raised position, spaced from the ground surface. This limited use of the wheels is provided, however, when the wheelchair is in a tilted back position, such that the wheelchair is supported on the ground by its main travel wheels and a rear-located roller forming part of the wheelchair carrier.
U.S. Pat. No. 4,411,330 describes stair climbing apparatus for a wheelchair or the like. The climbing apparatus, which travels on powered tracks, has a platform configured to permit the ascent and support thereon of a wheelchair, for example, such that the carrier, together with the wheelchair and a person seated thereon, may be driven along a stairway. The wheelchair must be removed from the climbing apparatus before wheeled travel can be resumed.
U.S. Pat. No. 3,869,011 and published European Patent Application No. 0,299,839 relate to tracked vehicles having no facility for wheeled travel.
The following publications relate to wheelchairs having a stair climbing ability provided by other than tracked means: U.S. Pat. Nos. 3,269,478; 3,438,641; 3,592,282; and 4,569,409.